1. Field of the Invention
The present invention relates to an image forming method, an ink-jet recording method and instruments used in such methods.
2. Related Background Art
An ink-jet recording method is a system in which droplets of an ink are ejected to apply the ink to a recording (printing) medium such as paper, thereby conducting recording. In particular, according to the ink-jet recording method of the system disclosed in Japanese Patent Publication Nos. 61-59911, 61-59912 or 61-59914, in which an electrothermal converter is used as an ejection-energy supply means X apply thermal energy to an ink so as to generate bubble thereby ejecting droplets of the ink, the formation of high-density multi-orifice recording head can be realized with ease, and high-resolution and high-quality images can be recorded at high speed.
However, inks used in the conventional ink-jet recording methods generally comprise, as a principal component, water, and include additionally a water-soluble high boiling solvent such as glycol for the purpose of preventing drying and clogging at orifices, and the like. When such an ink has been used to conduct recording on plain paper, there have been experienced such problems that fixing ability cannot be sufficiently achieved, and image irregularity occurs, which is attributed to the uneven distribution of a filler and a size of the surface of the recording paper. In particular, when it is intended to form color images, plural inks of different colors are overlapped one after another before an ink of a certain color is fixed to the recording paper. Therefore, color bleeding and uneven color mixing have occurred at portions of boundaries between images of different colors (this phenomenon will hereinafter be referred to as "bleeding" simply), resulting in a failure to obtain satisfactory images.
As a means for enhancing fixing ability of inks, Japanese Patent Application Laid-Open No. 55-65269 discloses the addition of a compound capable of enhancing penetrability, such as a surfactant, to the inks. Besides, Japanese Patent Application Laid-Open No. 55-66976 discloses the use of inks comprising, as a principal component, a volatile solvent. However, the former method, in which the surfactant is added to the inks, has involved a disadvantage that although the penetrability of the inks into recording paper is improved, and so the fixing ability and anti-bleeding property of the inks are improved to some extent, the optical density and saturation of the resulting image are lowered because coloring materials contained in the inks also penetrate deeply into the recording paper. In addition, the inks have also involved a problem that they spread in lateral directions, resulting in reduction of edge sharpness and resolution. On the other hand, the latter method, in which the inks comprising, as a principal component, the volatile solvent are used, has been liable to cause clogging due to the evaporation of the solvent in a nozzle of a recording head in addition to the above-described disadvantages attendant on the former method. Such methods have hence not been preferred.
In order to improve the above-described problems, there have been further proposed methods in which a liquid capable of making the quality of images better is applied in advance to a recording medium prior to ejection of an ink.
For example, Japanese Patent Application Laid-Open No. 63-299971 discloses a method in which a liquid comprising an organic compound having two or more cationic groups per molecule is applied to a recording medium, and recording is then conducted with inks comprising an anionic dye. Japanese Patent Application Laid-Open No. 64-9279 discloses a method in which an acidic liquid containing succinic acid is applied to a recording medium, and recording is then conducted with inks comprising an anionic dye. Further, Japanese Patent Application Laid-Open No. 64-63185 discloses a method in which a liquid, which insolubilizes dyes, is applied to a recording medium prior to recording.
However, these methods involve a peculiar problem liable to arise in the case where heads for separately ejecting a liquid composition and an ink, which respectively contain substances different in polarity from each other (the difference in polarity as referred to herein means a difference between anionic and cationic polarities; when both substances different in polarity are mixed, a reaction takes place between the anionic and cationic sites of such substances to form an aggregate insoluble in water), are situated in the vicinity of each other.
When an ink ejected from a head flies in the form of spray in the air and adheres to a face of a head for ejecting another ink different in polarity, the face becomes liable to stain. Such a phenomenon becomes marked when it is intended to print an image high in printing duty.
Therefore, when such images are continuously printed, it is necessary to devise how to wipe the face, such as increasing the number of wipings, resulting in an offer of problems such as reduction in throughput and increase in cost.